The latest update to iOS has been rolled out to iPhone 5 devices.
This 6.1.4 version is expected to be the last iteration until the reveal of iOS 7 next month.
No new features have been added but an update to the audio ‘profile for speakerphone’ has been found. It is usual for Apple to add security updates but given the surprise nature of the update, the release seems absent of these.
The release was published OTA (over the air) so keep your eyes out for it.